Hi,
1. It should not be a problem as far as you can ensure that the traffic will flow back thru the CSS to avoid asymmetric flows, also you need to make sure to open all the ports for traffic flowing between the CSS and the server. Anyway this is not a common design and would need to be test it to see if would work fine for you.
2. Yes the CSS11500 series do support NHI for a VIP.
Here are the requirements:
1) RHI on CSS11500 is implemented using OSPF, pre-requisites for this feature
include,
- Requires CSS11500 to have OSPF enabled globally
- Requires CSS11500 to be configured as ASBR 'ospf as-boundary'
- Use 'ospf advertise' command to advertise specific VIPs with /32 mask
- Requires OSPF to be enabled on Circuit connecting to neighbor router
- CSS VIP Master will advertise the VIP address, assuming all services and rule are active
Hope it helps!!